Field of the Invention
The present invention generally relates to mechanical equipment for use in farm implements. More particularly, the present invention relates to a gravitational latch for preventing wing lift wheels in tillage equipment from extending before the wings have completely unfolded.
Description of the Related Art
In farming, tillage machines are used for a variety of purposes. For instance, tillage machines may be used to loosen the soil, mix in fertilizer, shape fields into rows, or generally prepare a field for seeding. A typical tillage machine may have wings on which various farm implements are mounted and wing wheels to support the wings. Modern tillage machines can be massive machines that perform the field preparation over a large area. While having machines of large size is an advantage during tillage, it can make the tillage machines unwieldy during transportation to or from a field. Accordingly, most modern tillage machines can fold from a wide working position to a more compact transport position.
To accomplish the folding from a wide working position to the more compact position, a tillage machine might have a base frame and two folding wings that are folded from the working position to the compact position with the aid of a hydraulic system. The wings may be folded in a variety of different ways. One common way to fold wings involves folding two wings in a crossing pattern with very little clearance between the wings. Each wing may be equipped with a wing lift wheel for raising the wing to turn on the ends of a field or to hold a constant working depth for the machine. The wing lift wheels are frequently retracted by a hydraulic system when the tillage machine is in the transport position and extended only when the tillage machine is unfolded into the working position.
For reasons of economy, it is typically desirable to have a single hydraulic system that controls both the folding/unfolding of the wings and the retraction/extension of the wing lift wheels. A problem associated with the using a single hydraulic system, however, is the risk that the wing lift wheels will extend too quickly as the wings unfold. When this happens, the wing lift wheel of one wing can come into contact with the other wing thereby causing damage to the tillage machine.
Methods of preventing the wing lift wheel from extending before the wings have been completely unfolded are known. One method involves providing a hydraulic lockout valve to lock the hydraulic valve that extends the wing lift wheel thereby preventing it from prematurely extending. Another method involves providing a cylinder transport lock to physically prevent the hydraulic valve that extend the wing lift wheels from moving, thereby preventing the wing lift wheel assembly from extending. Both of these methods have the disadvantage that the operator is required to leave the tractor and physically operate either a lockout valve or a transport lock. It is undesirable to require the operator to leave the tractor because it takes unnecessary effort and time.
Thus, there exists the need for an improved system for preventing the wing lift wheel from extending before the wings have completely unfolded that does not require the operator to leave the tractor.